411 REFERENCE · Wikibooks
Chess Opening Theory/1. e4/1...e5/2. Nf3/2...d6/3. d4/3...Nd7/4. Bc4/4...Ngf6/5. dxe5/5...dxe5/6. Ng5
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
Hanham variation C41 Philidor defence → Hanham variation → 5...dxe5
6. Ng5
Black cannot guard f7. White threatens Bxf7+ Ke7 Ne6 and Black's queen is trapped.
6...Nb6 is the best attempt. 7. Bxf7+ Ke7 8. Qxd8+ Kxd8+++ White is up a pawn in an endgame. Bb3 and Nf7+ forking the king, rook and pawn is threatened.
6...Bb4+ at least allows Black to castle if they give up the bishop. 7. c3 O-O 8. cxb4.
References
See also